login
A047463
Numbers that are congruent to {2, 4} mod 8.
9
2, 4, 10, 12, 18, 20, 26, 28, 34, 36, 42, 44, 50, 52, 58, 60, 66, 68, 74, 76, 82, 84, 90, 92, 98, 100, 106, 108, 114, 116, 122, 124, 130, 132, 138, 140, 146, 148, 154, 156, 162, 164, 170, 172, 178, 180, 186, 188, 194, 196, 202, 204, 210, 212, 218, 220, 226, 228, 234
OFFSET
1,1
COMMENTS
First differences in A010696.
FORMULA
a(n) = 8*n - a(n-1) - 10, with a(1)=2. - Vincenzo Librandi, Aug 06 2010
From Bruno Berselli, May 11 2011: (Start)
G.f.: 2*x*(1+x+2*x^2)/((1+x)*(1-x)^2).
a(n) = 4*n-(-1)^n-3.
Sum_{i=1..n} a(i) = 2*A014848(n).
a(n) = 2*A042963(n-1). (End)
Sum_{n>=1} (-1)^(n+1)/a(n) = Pi/16 + log(2)/8. - Amiram Eldar, Dec 18 2021
MATHEMATICA
Select[Range[250], MemberQ[{2, 4}, Mod[#, 8]] &] (* Amiram Eldar, Dec 18 2021 *)
PROG
(Magma) [ n: n in [2..234 by 2] | n mod 8 in [2, 4] ]; // Bruno Berselli, May 11 2011
CROSSREFS
Union of A017089 and A017113.
Cf. A014848.
Sequence in context: A081887 A085344 A288225 * A107059 A160716 A071642
KEYWORD
nonn
EXTENSIONS
More terms from Vincenzo Librandi, Aug 06 2010
STATUS
approved